Term simple expenditure multiplier Definition: The ratio of the change in aggregate output (or gross domestic product) to an autonomous change in an aggregate expenditure (consumption expenditures, investment expenditures, government purchases, or net exports) when consumption is the only induced expenditure. This is the least complicated expenditure multiplier possible, based exclusively on induced consumption, and is the inverse of the marginal propensity to save. This simple multiplier becomes more complicated by adding other induced expenditures.